And for information about how babies fall asleep--and how you can help your baby stay asleep--see this article about the biology of baby sleep.

How baby sleep requirements are estimated

Everybody knows that babies need more sleep than older children do. But how much?

When I began researching baby sleep requirements, I assumed that
those authoritative charts we see published everywhere—the ones telling
us that the average newborn needs 16 hours of sleep, for example—were
based on scientifically-established, biological needs.

I figured that somebody must have identified a link between, say,
a certain minimum number of sleep hours and optimal rates of childhood
growth. Or between sleep hours and rates of infection.

I was wrong.

It turns out that scientists know relatively little about baby
sleep requirements. The sleep charts that you see in parenting books
and websites are based on how much time parents—typically, Western parents—say their babies spend sleeping. For instance, studies of Australian babies reveal that the average newborn gets about 16-17 hours of sleep over a 24-hour period. Babies aged 4-6 months average 14 hours (So et al 2007; Price et al 2014).

Do such average sleep times predict your baby’s sleep requirements?

Maybe. It seems plausible that most infants are pretty good
self-regulators of their own sleep needs. Give your baby enough
opportunities, and he may naturally meet his own baby sleep
requirements. If that's true—and if most parents give their babies the
necessary opportunities—then studies of real-world sleep behavior may
tell us a lot about baby sleep requirements.

But it's a bit more complicated than that.

For one thing, different individuals have different needs. This
may be especially true for baby sleep requirements. As the data below
show, babies vary tremendously in the number of hours that they sleep.

Another important point is that sleep habits vary from culture
to culture. Children in living in different nations get different
amounts of sleep, and average sleep times have changed from generation
to generation.

Based on a recent telephone survey conducted by the National
Sleep Foundation, American kids—including babies—seem to be sleeping
less than they used to (National Sleep Foundation 2004).

Are contemporary kids in these countries getting the right amount
of sleep? Some researchers suspect not. But until more research has
been done, nobody knows for sure.

So sleep charts are not necessarily the last word on baby sleep
requirements. To estimate your baby’s own, individualized needs, you
need to supplement information from sleep charts with your own
observations of your baby’s behavior.

Below I provide detailed data from one of the best modern studies of
average sleep times (Iglowstein et al 2003). As you check the numbers
out, be sure to notice how widely sleep times vary for each age group.

Baby sleep requirements: Evidence from a longitudinal study

Iglowstein and colleagues tracked 493 Swiss children from birth to 16
years (Iglowstein et al 2003). Here are the sleep patterns they
observed for children under the age of 2 years. They may serve as a
rough guide to baby sleep requirements.

1 month old:

The average baby got a total of 14-15 hours of sleep

50% of babies got between 13 and 16 hours

96% of babies got between 9 and 19 hours

3 months old:

The average baby got a total of 14-15 hours of sleep

50% of babies got between 13 and 16 hours

96% of babies got between 10 and 19 hours

6 months old:

The average baby got about 14.2 hours of total sleep

50% of babies got between 13 and 15.5 hours

96% of babies got between 10.4 and 18.1 hours

9 months old:

The average baby got about 13.9 hours of total sleep

50% of babies got between 12.8 and 15 hours

96% of babies got between 10.5 and 17.4 hours

1 year old:

The average baby got about 13.9 hours of total sleep

50% of babies got between 13 and 14.8 hours

96% of babies got between 11.4 and 16.5 hours

18 months old:

The average baby got about 13.6 hours of total sleep

50% of babies got between 12.7 and 14.5 hours

96% of babies got between 11.1 and 16 hours

2 years old:

The average baby got about 13.2 hours of total sleep

50% of babies got between 12.3 and 14 hours

96% of babies got between 10.8 and 15.6 hours

These numbers represent total sleep duration--how much babies
slept over a 24-hour period. Of course, not all of this sleep time
occurred at night.

One-month-old babies slept an average of 8 hours each night, with
96% of babies getting between 6 and 13.3 hours of nighttime sleep. At 3
months, babies spent more time sleeping at night--10 hours, on average.
For babies over 6 months, the amount of nighttime sleep stayed fairly
constant across ages—about 11 hours on average, with a range of
approximately 9-13 hours (Iglowstein et al 2003).

Baby sleep requirements are also met by sleeping during the day.
Here is some information on the amount of time babies spent taking naps.

Daytime sleep (naps)

In the Swiss study (Iglowstein et al 2003), all babies took naps
throughout their first year. Most babies continued the practice of
napping throughout their second year, with 87% of 2-year olds taking
daytime naps. Time spent napping followed these patterns:

1 month old

The average baby slept between 5 and 6 hours during the daytime

50% of babies slept between approximately 4.5 and 7 hours

96% of babies slept between 2 and 9 hours

3 months old

The average baby slept a bit less than 5 hours during the daytime

50% of babies slept between approximately 3.5 and 6 hours

96% of babies slept between 1 and 8 hours

6 months old

The average baby slept about 3.4 hours during the daytime

50% of babies slept between approximately 2.5 and 4.5
hours

96% of babies slept between 0.4 and 6.4 hours

9 months old

The average baby slept about 2.8 hours during the daytime

50% of babies slept between approximately 2 and 4 hours

96% of babies slept between 0.2 and 5.3 hours

1 year old

The average baby slept about 2.4 hours during the daytime

50% of babies slept between approximately 2 and 3.5 hours

96% of babies slept between 0.2 and 4.6 hours

18 months old

The average baby slept about 2 hours during the daytime

50% of babies slept between approximately 1.5 to 2.5
hours

96% of babies slept between 0.5 and 3.6 hours

2 years old

The average baby slept about 1.8 hours during the daytime

50% of babies slept between approximately 1.3 to 2.3
hours

96% of babies slept between 0.7 and 2.9 hours

Elsewhere, naps may be on the decline. In a recent study of
American children, 82% of babies over 18 months were not taking any naps
on some or all days (Acebo et al 2005).

Baby sleep requirements: Why your baby may differ from the average

The statistics presented above represent some of the best research we
have on average sleep times for children. But before you try to apply
them to your own baby, keep in mind that the study focused on a specific
population: Swiss kids born between 1974 and 1993.

Depending on cultural factors and individual differences, baby
sleep patterns might differ significantly from those of the Swiss study
population. Consider these points.

Sleep times vary cross-culturally.

In one study,
sixteen-week old Kokwet babies—members of the Kipsigi ethnic group in
Kenya—slept about 2 hours less per 24 hours than did American babies of
the same age (Super and Harkness 1982; Parmalee et al 1964). In another
study, 3-month old Dutch infants slept 2 hours more than American
infants did (Super et al 1996). Such cultural differences in sleep
duration may reflect important differences in the ways that babies are
handled and fed during the day. For instance, American parents believe
it is especially important to provide their babies with lots of sensory
stimulation. Dutch parents are more likely to emphasize rest and
regularity (Super et al 1996).

Breastfed babies tend to sleep less.

Studies of 4
week-old infants found that breastfed babies got less sleep than did
formula-fed babies (Quillin and Glenn 2004; Quillin 1997).

Cosleeping babies sleep less.

A Swiss study has reported
that children over 9 months of age who shared their parents’ beds slept
less than did children who slept alone (Jenni et al 2005).

Every baby is different.

As the data above indicate,
babies may vary greatly in the amount of time that they sleep. And
recent research suggests that some variation in individual sleep
patterns has a biological basis. Adults subjected to identical sleep
conditions respond in individualistic ways—even when they all belong to
the same culture (Tucker et al 2007). Recent genetic research indicates
that some aspects of sleep--including sleep duration--have a genetic
basis (Gottlieb et al 2007). Baby sleep requirements may run
in the family.

Coping with the individualized nature of baby sleep requirements

The charts above offer clues to your infant’s sleep needs. But for a
more fine-tuned estimate of baby sleep requirements, you need to
consider your baby’s behavior. You can learn a lot by observing what
time(s) of day she seems sleepy and what her behavior is like when she
wakes up in the morning.

Jenni OG, Zinggeler Fuhrer H, Iglowstein I, Molinari L, and Largo
RH. 2005. A longitudinal study of bed sharing and sleep problems among
Swiss children in the first 10 years of life. Pediatrics 115(1):
233-240.

So, K, Adamson TM, and Horne RS. 2007. The use of actigraphy for
assessment of the development of sleep/wake patterns in infants during
the first 12 months of life. Journal of Sleep Research 16(2): 181-187.